This project is attempting to determine whether caloric modification of the diets of rhesus and squirrel monkeys can affect aging rate as assessed by various physiological, biochemical and behavioral indices. Recent findings include data suggesting that calorie restriction improves risk factors for cardiovascular disease. Specifically, calorie restriction (CR) lowered serum triglycerides and increased levels of the HDL subfractions, HDL2b. Elevated serum levels of this particular subfraction have been associated with decreased heart disease in humans. Previous data from the project have shown that CR decreases blood glucose and insulin levels and suggested that CR might also delay or reduce diabetes. Thus, it appears likely that even if CR does not markedly extend lifespan in primates, moderate lifespan increases due to effects of CR on diabetes and cardiovascular disease will be observed. Recently, we have expanded our use of a short-term CR paradigm. These studies arose from our previous findings that body temperature and energy expenditure were reduced during adaptation to CR. Results demonstrated that metabolic changes which could be related to the underlying biological mechanism of CR occurred a few months after CR was initiated. The primary focus of these short-term studies is to assess possible metabolic mechanisms of CR. Currently there are 3 groups of monkeys on short-term studies: 2 young groups (1 male and 1 female) and 1 old male group. In addition to metabolic studies, measurements in the old monkeys will be directed at evaluating the progression of several age-related diseases including diabetes and cardiovascular disease.